1. Field of the Invention
The present invention relates to injection molding machines and, more particularly, to a safety cover for the die closing unit of an injection molding machine which has jointly or separately operable safety gates on three sides of the die closing unit, cooperating with electrical and hydraulic safety interlock devices which block the operation of the die closing unit, when a safety gate is moved from its closed position.
2. Description of the Prior Art
Injection molding machines require a safety cover surrounding the die closing unit, in order to prevent access to the injection molding die, when the machine is in operation. Several types of safety covers which are equipped with appropriate electrical, hydraulic and/or mechanical interlock devices are known from my German Pat. Nos. 20 20 061, 21 46 042 and 25 28 907 and corresponding U.S. Pat. Nos. 3,744,949; 3,804,003 and 4,113,414, as well as from U.S. Pat. Nos. 3,386,133 and 3,728,057. The majority of these prior art solutions suggest a U-shaped safety cover which is guided for movement along stationary rods, in parallel alignment with the axis of the die closing unit.
Only the structure suggested in U.S. Pat. No. 3,744,949 provides for the cover assembly to be constituted by three separate cover panels which can be adjusted for separate mobility, so that only the front panel opens, for example, for limited quick access to the injection molding die. This solution, however, requires two stationary guide rods for each of the three cover panels, where a rigid U-shaped cover requires only two guide rods, one on each side of the die closing unit.
What all prior art safety covers have in common is that their cover guide rods extend across the entire length of the injection molding die, having one extremity attached to the stationary die carrier plate. These guide rods represent an obstacle for certain operations involving the injection molding die, especially for the use of devices which are designed for the mechanized insertion and removal of injection molding dies.
Another shortcoming of the various prior art solutions is that their safety interlock devices are mounted on various stationary components of the die closing unit and that, in most cases, the control rods which operate these safety devices protrude axially from the safety covers, thus representing a safety hazard and taking up valuable space.